1. Field of the Invention
The invention relates to alkoxy-crosslinking one-component sealant materials based on alkoxyorganosilane-terminated polymers having an outstanding shelf-life and outstanding curing characteristics.
2. Description of the Related Art
Organic polymers having terminal silane groups in the form of one-component materials curing with atmospheric humidity (RTV-1) are known and are widely used for the preparation of flexible sealants and adhesives. Such polymers may be composed of different building blocks. Usually, these are polyurethanes, polyethers, polyesters, polyacrylates, polyvinyl esters, ethylene/olefin copolymers, styrene/butadiene copolymers or polyolefins. It is known that, for stabilization during the processing and storage of the compounds, low molecular weight compounds which have hydrolyzable groups which have a higher reactivity to water than the silane-terminated polymers are added to these one-component materials. The amount of added water scavengers depends on the water content of the components of the formulation and on the desired shelf-lives and processing times. In general, these are organofunctional silanes, the organic radical often being critical for the reactivity. Examples of such silanes are vinyltrimethoxysilane and alkylaminopropyltrimethoxysilanes, but also, for example, silanes which bind water with the formation of ammonia, such as hexamethyldisilazane.
In general, substituted propyltrimethoxysilanes are used for the termination since they are as a rule economically available and have very good reactivity in the materials. However, owing to the high reactivity, the polymers are also problematic with regard to processing, for example in the incorporation of water-containing fillers or additives which increase the reactivity further; moreover, the shelf-lives are often insufficient.
For example, the addition of relatively large amounts of aminosilanes as adhesion promoters can greatly reduce the shelf-life. The materials generally have to be stabilized by means of further added components, such as, for example, the phosphoric esters described in DE-A-19923300, in order to moderate the catalyst activity. Furthermore, the addition of standard water scavengers, such as vinyltrimethoxysilane, is suitable only to a limited extent for stabilizing the materials.
Analogously to the organic polymers already described above, polydiorganosiloxanes having high reactivities are also known. U.S. Pat. No. 5,254,657 describes moisture-curing silicone-based materials in which the crosslinkable silane units are prepared analogously to the organic polymers via the reaction of an aminosilicone with an isocyanatoalkylalkoxysilane. These too have a problematic shelf-life owing to the high reactivity of the terminal silane groups.